The first thing to consider is the parts you want to produce. The key point is to buy a machine that can complete the processing task with the shortest workbench and the smallest tonnage.

Carefully consider the material grade and the maximum processing thickness and length. If most of the works are low carbon steel, the thickness is 16, and the maximum length is 10 feet, the free bending force need not be greater than 50 tons. But if you are engaged in forming a large number of concave dies with bottoms, maybe you should consider a 150 tonnage machine tool.

Well, suppose the thickest material is 65,438+0/4 inch, the free bending at 65,438+000 feet is 65,438+065 tons, and the bending (correction bending) with the bottom die is at least 600 tons. If most of the workpieces are 5 feet or shorter, the tonnage will be almost halved, thus greatly reducing the procurement cost. The length of the parts is very important to determine the specifications of the new machine.

be partial to

You should also consider the possible deviation of this machine. Under the same load, the deflection of the workbench and slider of the 10 pin machine is four times that of the 5 pin machine. In other words, shorter machines require less gasket adjustment to produce qualified parts. Reducing gasket adjustment shortens the preparation time.

Material grade is also a key factor. Compared with low carbon steel, the load required by stainless steel usually increases by about 50%, while the soft aluminum of most brands decreases by about 50%. You can always get the tonnage table of the machine from the manufacturer of the bending machine, which shows the tonnage estimation required per foot length under different thicknesses and materials.

Bending radius of parts

Next, we must pay attention to the bending radius of the parts.

When free bending is used, the bending radius is 0. 156 times of the mold opening distance. In the process of free bending, the opening distance of the female die should be 8 times of the thickness of the metal material. For example, when 16 mild steel is formed with an opening distance of 1/2 inches, the bending radius of the part is about 0.078 inches. If the bending radius is almost as small as the thickness of the material, it must be formed by female die with a bottom. However, the pressure required to form a female die with a bottom is about 4 times greater than that required for free bending.

If the bending radius is less than the thickness of the material, a punch with the radius of the front fillet less than the thickness of the material should be adopted and the stamping bending method should be resorted to. Thus, a free bending pressure of 10 times is required.

As far as free bending is concerned, the punch and die are machined at an angle of 85 or less (the smaller the better). When using this set of dies, we should pay attention to the clearance between the punch and the die at the bottom of the stroke and the excessive bending enough to compensate the rebound, and keep the material at about 90.

Generally, the springback angle of the free bending die on the new bending machine is ≤ 2, and the bending radius is equal to 0. 156 times the die opening distance.

For the bending of a concave die with a bottom, the die angle is generally 86 ~ 90. At the bottom of the stroke, there should be a gap slightly larger than the thickness of the material between the convex and concave dies. The forming angle is increased, because the tonnage of bottom die bending is large (about 4 times that of free bending), which reduces the stress that usually causes springback within the bending radius.

The stamping bending is the same as that of the bottomed female die, except that the front end of the punch is machined to the required bending radius, and the gap between the punch and the female die at the bottom of the stroke is less than the material thickness. Because enough pressure (about 10 free bending) is applied to force the front end of the punch to contact the material, rebound is basically avoided.

In order to choose the specification with the lowest tonnage, it is best to plan the bending radius larger than the material thickness and adopt the free bending method as far as possible. When the bending radius is large, it often does not affect the quality of finished products and future use.

accurate

The requirement of bending accuracy is a factor that needs careful consideration. It is this factor that determines whether you need to consider CNC bending machine or manual bending machine. If the bending accuracy requires 1 and cannot be changed, you must focus on CNC machine tools.

The repetitive precision of the slider of the CNC bending machine is 0.0004 inch, so it is necessary to use such precision and a good mold to form an accurate angle. The repetitive precision of the slide block of the manual bending machine is 0.002 inch, and the deviation of 2 ~ 3 will generally occur when the appropriate die is used. In addition, the CNC bending machine is ready for rapid mold assembly, which is undoubtedly considered when you need to bend many small batch parts.

mould

Even if you have a shelf full of molds, don't think that these molds are suitable for newly bought machines. The wear of each die must be checked by measuring the length from the front end of the male die to the shoulder and the length between the shoulders of the female die.

For traditional molds, the deviation per foot should be about 0.00 1 inch, and the total length deviation should not exceed 0.005 inch. As for the fine grinding mold, the accuracy per foot should reach 0.0004 inch, and the total accuracy should not be greater than 0.002 inch. It is best to use fine grinding die for numerical control bending machine and conventional die for manual bending machine.

In fact, we often make the mistake of buying a new bending machine, but there is no suitable mold to match it.

Side length of curved part

One factor that people often ignore is the length of the bending edge of the material in front of the bending machine.

Assuming that the low-carbon steel plate is bent 90 degrees along the 5× 10 gauge, the bending machine must apply an additional pressure of 7.5 tons to jack up the steel plate, and the operator must be prepared to fall 280 pounds straight. It may take several strong workers or even a crane to make this part. Bending machine operators often need to bend long parts, but they don't realize how hard their work is.

At present, there is a material supporting device suitable for workshops engaged in this kind of work, which can be improved according to the needs of new and old machines. With this device, only one person is needed to operate the long side part.